1. Field of the Invention
The present invention relates generally to a track roller. In particular, the present invention relates to a self-lubricating track roller with a resilient tire bonded to an outer ring.
2. Description of the Related Art
Conventional track rollers use internal rolling elements, such as needles, to allow the rotation of one of the roller rings relative to the other. To work effectively, the rolling elements are often coated with a lubricant supplied by an external source. However, in environments with extreme temperatures or chemical contamination, an external lubrication source is not always practical. In an attempt to address some of the deficiencies of external lubrication sources, self-lubricating track rollers have been developed.
For example, U.S. Pat. No. 5,398,294 discloses a track roller with a self-lubricating material bonded to the inner ring. The track roller is created by injecting the self-lubricating material between the inner ring and an outer ring and then curing the self-lubricating material. The inner ring may be swaged to form inclined axial bearing surfaces. During use, these surfaces will resist axial forces that could cause separation of the inner ring and the outer ring.
Yet another self-lubricating track roller is disclosed in U.S. Pat. No. 4,685,184. This track roller includes a self-lubricating liner material bonded via adhesive to a radially outwardly facing surface of an inner ring. A heat shrinkable tubing assembly fixture is used to securely adhere the self-lubricating liner material to the inner ring. The inner ring is then assembled with an outer ring to form a self-lubricating track roller.
To be effective, the components of self-lubricating track rollers must be precisely formed. Unless the self-lubricating track rollers maintain this precision, their service life will be shortened. Even minor defects from fabrication or use can result in irreparable damage to the roller, requiring it to be taken out of service.
For example, self-lubricating track rollers are particularly susceptible to binding as a result of contamination or abrasion at the sliding interface (i.e., the interface between the self-lubricating surface and the adjacent sliding surface). If the friction at the sliding interface exceeds the friction between the surfaces at other roller interfaces, then the surfaces at the other roller interfaces may slide past one another causing undesired wear damage. For example, such wear damage may occur at the interface between two components of the track roller or between the track roller and the object that the track roller is transporting (i.e., a conveyor belt or an object being directly transported on the track roller). In either case, the binding at the sliding interface results in damage to the track roller or another item in the motive assembly.
Additionally, track rollers are commonly subjected to vibrations and oscillations that may result in fretting or corrosion damage. These vibrations and oscillations can occur from the use of the track roller itself, the use of other machines in the vicinity of the track roller, or both. If the track roller is stationary when it is subjected to vibration, then the vibration can cause the selective degradation of a portion of the surface at the sliding interface. This selective degradation in turn may create asymmetries along the sliding interface that can interrupt the smooth rotation of the roller or provide a gap that permits contaminants to encroach on the sliding interface.
Although treatments exist that prevent corrosion and fretting damage to bearings, these treatments are typically only applicable to externally-lubricated rollers. For example, U.S. Pat. No. 7,176,167 discloses a vibration resistant bearing that uses rust preventative oil. The oil contains a high-pressure organic additive that protects the bearing from damage due to vibrations. U.S. Pat. Pub. No. 2006/0088235 discloses a bearing having fretting resistance. Specifically, the roller bearing components are subjected to carbonitriding to provide fretting resistance.
Hence, a need exists for a self-lubricated track roller that does not require an external lubrication source, but is less susceptible to damage by sliding contact, corrosion, and fretting.